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Kuypers KLAM, Dekker J, Crossley KJ, Wallace MJ, Cramer SJE, Davies IM, Jurkschat D, Kitchen MJ, Te Pas AB, Hooper SB. Slowing lung deflation by increasing the expiratory resistance enhances FRC in preterm rabbits. Pediatr Res 2024:10.1038/s41390-024-03388-w. [PMID: 38977795 DOI: 10.1038/s41390-024-03388-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/16/2024] [Revised: 06/14/2024] [Accepted: 06/21/2024] [Indexed: 07/10/2024]
Abstract
BACKGROUND As very preterm infants have surfactant-deficient and highly incompliant lungs, slowing lung deflation during expiration might help preserve functional residual capacity(FRC) during lung aeration. In this study, we investigated the effect of expiratory resistance(Re) on lung aeration during positive pressure ventilation in preterm rabbits immediately after birth. METHODS Preterm rabbit pups were delivered at 29 days gestation, mechanically ventilated from birth and simultaneously imaged to measure lung aeration using phase-contrast X-ray. Re was varied by altering the length (0, 60 or 1000 mm) of the expiratory circuit. RESULTS Increasing Re led to a decrease in lung deflation rates and both peak expiratory flows and flow rates at mid-deflation. As a result, the rate of de-acceleration(slowing) in lung deflation when approaching FRC was markedly reduced with increasing resistance. During lung aeration, FRC was significantly different between resistance groups and was significantly higher over time in the high compared to the low resistance group. While FRC values tended to be higher with higher Re, they were not significantly different at end-ventilation (t = 7 min). CONCLUSION Increasing Re of the ventilation circuit during lung aeration in preterm rabbits immediately after birth decreased lung deflation rates and increased the accumulation of FRC over time. IMPACT The expiratory phase of the ventilatory cycle has been largely overlooked as an opportunity to improve ventilation in preterm infants after birth. Increasing the expiratory resistance of the ventilator circuit during lung aeration in preterm rabbits immediately after birth markedly decreased lung deflation rates and increased FRC accumulation, compared to a low expiratory resistance. This indicates that ventilation devices that reduce the "work of breathing" by reducing the expiratory resistance, may have the unintended effect of reducing FRC, particularly in extremely preterm infants that have surfactant deficient highly incompliant lungs.
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Affiliation(s)
- Kristel L A M Kuypers
- Division of Neonatology, department of paediatrics, Willem-Alexander Children's Hospital, Leiden University Medical Centre, Leiden, the Netherlands.
| | - Janneke Dekker
- Division of Neonatology, department of paediatrics, Willem-Alexander Children's Hospital, Leiden University Medical Centre, Leiden, the Netherlands
| | - Kelly J Crossley
- The Ritchie Centre, Hudson Institute of Medical Research, Melbourne, VIC, Australia
- Department of Obstetrics and Gynaecology, Monash University, Melbourne, VIC, Australia
| | - Megan J Wallace
- The Ritchie Centre, Hudson Institute of Medical Research, Melbourne, VIC, Australia
- Department of Obstetrics and Gynaecology, Monash University, Melbourne, VIC, Australia
| | - Sophie J E Cramer
- Division of Neonatology, department of paediatrics, Willem-Alexander Children's Hospital, Leiden University Medical Centre, Leiden, the Netherlands
| | - Indya M Davies
- The Ritchie Centre, Hudson Institute of Medical Research, Melbourne, VIC, Australia
- Department of Obstetrics and Gynaecology, Monash University, Melbourne, VIC, Australia
| | - Dominic Jurkschat
- School of Physics and Astronomy, Monash University, Melbourne, VIC, Australia
| | - Marcus J Kitchen
- The Ritchie Centre, Hudson Institute of Medical Research, Melbourne, VIC, Australia
- School of Physics and Astronomy, Monash University, Melbourne, VIC, Australia
| | - Arjan B Te Pas
- Division of Neonatology, department of paediatrics, Willem-Alexander Children's Hospital, Leiden University Medical Centre, Leiden, the Netherlands
| | - Stuart B Hooper
- The Ritchie Centre, Hudson Institute of Medical Research, Melbourne, VIC, Australia
- Department of Obstetrics and Gynaecology, Monash University, Melbourne, VIC, Australia
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Cramer SJE, Dekker J, Croughan MK, Lee KL, Crossley KJ, McGillick EV, Martherus T, Thio M, Wallace MJ, Kitchen MJ, Hooper SB, Te Pas AB. The effect of vibrotactile stimulation on hypoxia-induced irregular breathing and apnea in preterm rabbits. Pediatr Res 2024; 96:325-331. [PMID: 38356025 DOI: 10.1038/s41390-024-03061-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/27/2023] [Revised: 12/22/2023] [Accepted: 12/29/2023] [Indexed: 02/16/2024]
Abstract
BACKGROUND Manual tactile stimulation is used to counteract apnea in preterm infants, but it is unknown when this intervention should be applied. We compared an anticipatory to a reactive approach using vibrotactile stimulation to prevent hypoxia induced apneas. METHODS Preterm rabbit kittens were prematurely delivered and randomized to either group. All kittens breathed spontaneously with a positive airway pressure of 8 cmH2O while they were imaged using phase contrast X-ray. Irregular breathing (IB) was induced using gradual hypoxia. The anticipatory group received stimulation at the onset of IB and the reactive group if IB transitioned into apnea. Breathing rate (BR), heart rate (HR) and functional residual capacity (FRC) were compared. RESULTS Anticipatory stimulation significantly reduced apnea incidence and maximum inter-breath intervals and increased BR following IB, compared to reactive stimulation. Recovery in BR but not HR was more likely with anticipatory stimulation, although both BR and HR were significantly higher at 120 s after stimulation onset. FRC values and variability were not different. CONCLUSIONS Anticipated vibrotactile stimulation is more effective in preventing apnea and enhancing breathing when compared to reactive stimulation in preterm rabbits. Stimulation timing is likely to be a key factor in reducing the incidence and duration of apnea. IMPACT Anticipated vibrotactile stimulation can prevent apnea and stimulate breathing effort in preterm rabbits. Anticipated vibrotactile stimulation increases the likelihood of breathing rate recovery following hypoxia induced irregular breathing, when compared to reactive stimulation. Automated stimulation in combination with predictive algorithms may improve the treatment of apnea in preterm infants.
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Affiliation(s)
- Sophie J E Cramer
- Willem-Alexander Children's Hospital, Department of Pediatrics, Division of Neonatology, Leiden University Medical Center, Leiden, the Netherlands.
| | - Janneke Dekker
- Willem-Alexander Children's Hospital, Department of Pediatrics, Division of Neonatology, Leiden University Medical Center, Leiden, the Netherlands
| | - Michelle K Croughan
- School of Physics and Astronomy, Monash University, Melbourne, VIC, Australia
| | - Katie L Lee
- School of Physics and Astronomy, Monash University, Melbourne, VIC, Australia
- School of Earth and Environmental Science, University of Queensland, Brisbane, QLD, Australia
| | - Kelly J Crossley
- The Ritchie Centre, Hudson Institute of Medical Research, Melbourne, VIC, Australia
- Department of Obstetrics and Gynecology, Monash University, Melbourne, VIC, Australia
| | - Erin V McGillick
- The Ritchie Centre, Hudson Institute of Medical Research, Melbourne, VIC, Australia
- Department of Obstetrics and Gynecology, Monash University, Melbourne, VIC, Australia
| | - Tessa Martherus
- Willem-Alexander Children's Hospital, Department of Pediatrics, Division of Neonatology, Leiden University Medical Center, Leiden, the Netherlands
| | - Martha Thio
- Women's Newborn Research Centre, The Royal Women's Hospital, Melbourne, VIC, Australia
- Centre of Research Excellence in Newborn Medicine, Murdoch Children's Research Institute, Melbourne, VIC, Australia
- Department of Obstetrics and Gynecology, University of Melbourne, Melbourne, VIC, Australia
| | - Megan J Wallace
- The Ritchie Centre, Hudson Institute of Medical Research, Melbourne, VIC, Australia
- Department of Obstetrics and Gynecology, Monash University, Melbourne, VIC, Australia
| | - Marcus J Kitchen
- School of Physics and Astronomy, Monash University, Melbourne, VIC, Australia
- The Ritchie Centre, Hudson Institute of Medical Research, Melbourne, VIC, Australia
| | - Stuart B Hooper
- The Ritchie Centre, Hudson Institute of Medical Research, Melbourne, VIC, Australia
- Department of Obstetrics and Gynecology, Monash University, Melbourne, VIC, Australia
| | - Arjan B Te Pas
- Willem-Alexander Children's Hospital, Department of Pediatrics, Division of Neonatology, Leiden University Medical Center, Leiden, the Netherlands
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Higher CPAP levels improve functional residual capacity at birth in preterm rabbits. Pediatr Res 2022; 91:1686-1694. [PMID: 34294868 DOI: 10.1038/s41390-021-01647-8] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/14/2021] [Revised: 06/03/2021] [Accepted: 06/17/2021] [Indexed: 11/08/2022]
Abstract
BACKGROUND Preterm infants are commonly supported with 4-8 cm H2O continuous positive airway pressures (CPAP), although higher CPAP levels may improve functional residual capacity (FRC). METHODS Preterm rabbits delivered at 29/32 days (~26-28 weeks human) gestation received 0, 5, 8, 12, 15 cm H2O of CPAP or variable CPAP of 15 to 5 or 15 to 8 cm H2O (decreasing ~2 cm H2O/min) for up to 10 min after birth. RESULTS FRC was lower in the 0 (6.8 (1.0-11.2) mL/kg) and 5 (10.1 (1.1-16.8) mL/kg) compared to the 15 (18.8 (10.9-22.4) mL/kg) cm H2O groups (p = 0.003). Fewer kittens achieved FRC > 15 mL/kg in the 0 (20%), compared to 8 (36%), 12 (60%) and 15 (73%) cm H2O groups (p = 0.008). While breathing rates were not different (p = 0.096), apnoea tended to occur more often with CPAP < 8 cm H2O (p = 0.185). CPAP belly and lung bulging rates were similar whereas pneumothoraces were rare. Lowering CPAP from 15 to 5, but not 15 to 8 cm H2O, decreased FRC and breathing rates. CONCLUSION In all, 15 cm H2O of CPAP improved lung aeration and reduced apnoea, but did not increase the risk of lung over-expansion, pneumothorax or CPAP belly immediately after birth. FRC and breathing rates were maintained when CPAP was decreased to 8 cm H2O. IMPACT Although preterm infants are commonly supported with 4-8 cm H2O CPAP at birth, preclinical studies have shown that higher PEEP levels improve lung aeration. In this study, CPAP levels of 15 cm H2O improved lung aeration and reduced apnoea in preterm rabbit kittens immediately after birth. In all, 15 cm H2O CPAP did not increase the risk of lung over-expansion (indicated by bulging between the ribs), pneumothorax, or CPAP belly. These results can be used when designing future studies on CPAP strategies for preterm infants in the delivery room.
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Brooks FJ, Gunsten SP, Vasireddi SK, Brody SL, Anastasio MA. Quantification of image texture in X-ray phase-contrast-enhanced projection images of in vivo mouse lungs observed at varied inflation pressures. Physiol Rep 2019; 7:e14208. [PMID: 31444862 PMCID: PMC6708057 DOI: 10.14814/phy2.14208] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2019] [Revised: 07/25/2019] [Accepted: 07/27/2019] [Indexed: 12/13/2022] Open
Abstract
To date, there are very limited noninvasive, regional assays of in vivo lung microstructure near the alveolar level. It has been suggested that x-ray phase-contrast enhanced imaging reveals information about the air volume of the lung; however, the image texture information in these images remains underutilized. Projection images of in vivo mouse lungs were acquired via a tabletop, propagation-based, X-ray phase-contrast imaging system. Anesthetized mice were mechanically ventilated in an upright position. Consistent with previously published studies, a distinct image texture was observed uniquely within lung regions. Lung regions were automatically identified using supervised machine learning applied to summary measures of the image texture data. It was found that an unsupervised clustering within predefined lung regions colocates with expected differences in anatomy along the cranial-caudal axis in upright mice. It was also found that specifically selected inflation pressures-here, a purposeful surrogate of distinct states of mechanical expansion-can be predicted from the lung image texture alone, that the prediction model itself varies from apex to base and that prediction is accurate regardless of overlap with nonpulmonary structures such as the ribs, mediastinum, and heart. Cross-validation analysis indicated low inter-animal variation in the image texture classifications. Together, these results suggest that the image texture observed in a single X-ray phase-contrast-enhanced projection image could be used across a range of pressure states to study regional variations in regional lung function.
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Affiliation(s)
- Frank J Brooks
- Department of Bioengineering, University of Illinois at Urbana-Champaign, Urbana, Illinois
| | - Sean P Gunsten
- Department of Internal Medicine, Washington University School of Medicine, St. Louis, Missouri
| | - Sunil K Vasireddi
- Heart and Vascular Center, MetroHealth Campus at Case Western Reserve University, Cleveland, Ohio
| | - Steven L Brody
- Department of Internal Medicine, Washington University School of Medicine, St. Louis, Missouri
| | - Mark A Anastasio
- Department of Bioengineering, University of Illinois at Urbana-Champaign, Urbana, Illinois
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5
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Leong AFT, Asare E, Rex R, Xiao XH, Ramesh KT, Hufnagel TC. Determination of size distributions of non-spherical pores or particles from single x-ray phase contrast images. OPTICS EXPRESS 2019; 27:17322-17347. [PMID: 31252944 DOI: 10.1364/oe.27.017322] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/18/2019] [Accepted: 04/25/2019] [Indexed: 06/09/2023]
Abstract
Although x-ray tomography is commonly used to characterize the three-dimensional structure of materials, sometimes this is impractical due either to limited time for data collection (such as in rapidly-evolving systems) or the need to limit the radiation exposure of the sample. In such situations, it is desirable to extract as much information as possible from a more limited data set. In this paper, we describe how to extract the size distribution of non-spherical pores (or, equivalently, particles) from single x-ray phase contrast imaging (XPCI). Because the pores overlap in projection, interpreting the images and extracting quantitative information about the size distribution is non-trivial. In this paper we extend a previously-developed Fourier-based framework for interpreting the speckle pattern of XPCI images from materials with spherical pores to the more challenging case of non-spherical pores. We develop an analytical expression for the XPCI image from a distribution of randomly-oriented ellipsoidal pores, and show that we can use this expression to extract quantitative information about the size distribution from single images. We discuss three approaches to evaluating this expression, corresponding to different assumptions about the nature of the size distribution, and validate our results with simulated XPCI images and experimental data from Berea sandstone.
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6
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Dekker J, Hooper SB, Croughan MK, Crossley KJ, Wallace MJ, McGillick EV, DeKoninck PLJ, Thio M, Martherus T, Ruben G, Roehr CC, Cramer SJE, Flemmer AW, Croton L, Te Pas AB, Kitchen MJ. Increasing Respiratory Effort With 100% Oxygen During Resuscitation of Preterm Rabbits at Birth. Front Pediatr 2019; 7:427. [PMID: 31696099 PMCID: PMC6817611 DOI: 10.3389/fped.2019.00427] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/29/2019] [Accepted: 10/07/2019] [Indexed: 11/13/2022] Open
Abstract
Background: Spontaneous breathing is essential for successful non-invasive respiratory support delivered by a facemask at birth. As hypoxia is a potent inhibitor of spontaneous breathing, initiating respiratory support with a high fraction of inspired O2 may reduce the risk of hypoxia and increase respiratory effort at birth. Methods: Preterm rabbit kittens (29 days gestation, term ~32 days) were delivered and randomized to receive continuous positive airway pressure with either 21% (n = 12) or 100% O2 (n = 8) via a facemask. If apnea occurred, intermittent positive pressure ventilation (iPPV) was applied with either 21% or 100% O2 in kittens who started in 21% O2, and remained at 100% O2 for kittens who started the experiment in 100% O2. Respiratory rate (breaths per minute, bpm) and variability in inter-breath interval (%) were measured from esophageal pressure recordings and functional residual capacity (FRC) was measured from synchrotron phase-contrast X-ray images. Results: Initially, kittens receiving 21% O2 had a significantly lower respiratory rate and higher variability in inter-breath interval, indicating a less stable breathing pattern than kittens starting in 100% O2 [median (IQR) respiratory rate: 16 (4-28) vs. 38 (29-46) bpm, p = 0.001; variability in inter-breath interval: 33.3% (17.2-50.1%) vs. 27.5% (18.6-36.3%), p = 0.009]. Apnea that required iPPV, was more frequently observed in kittens in whom resuscitation was started with 21% compared to 100% O2 (11/12 vs. 1/8, p = 0.001). After recovering from apnea, respiratory rate was significantly lower and variability in inter-breath interval was significantly higher in kittens who received iPPV with 21% compared to 100% O2. FRC was not different between study groups at both timepoints. Conclusion: Initiating resuscitation with 100% O2 resulted in increased respiratory activity and stability, thereby reducing the risk of apnea and need for iPPV after birth. Further studies in human preterm infants are mandatory to confirm the benefit of this approach in terms of oxygenation. In addition, the ability to avoid hyperoxia after initiation of resuscitation with 100% oxygen, using a titration protocol based on oxygen saturation, needs to be clarified.
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Affiliation(s)
- Janneke Dekker
- Division of Neonatology, Department of Pediatrics, Leiden University Medical Center, Leiden, Netherlands.,The Ritchie Centre, Hudson Institute of Medical Research, Melbourne, VIC, Australia
| | - Stuart B Hooper
- The Ritchie Centre, Hudson Institute of Medical Research, Melbourne, VIC, Australia.,Department of Obstetrics and Gynaecology, Monash University, Melbourne, VIC, Australia
| | - Michelle K Croughan
- School of Physics and Astronomy, Monash University, Melbourne, VIC, Australia
| | - Kelly J Crossley
- The Ritchie Centre, Hudson Institute of Medical Research, Melbourne, VIC, Australia.,Department of Obstetrics and Gynaecology, Monash University, Melbourne, VIC, Australia
| | - Megan J Wallace
- The Ritchie Centre, Hudson Institute of Medical Research, Melbourne, VIC, Australia.,Department of Obstetrics and Gynaecology, Monash University, Melbourne, VIC, Australia
| | - Erin V McGillick
- The Ritchie Centre, Hudson Institute of Medical Research, Melbourne, VIC, Australia.,Department of Obstetrics and Gynaecology, Monash University, Melbourne, VIC, Australia
| | - Philip L J DeKoninck
- The Ritchie Centre, Hudson Institute of Medical Research, Melbourne, VIC, Australia.,Department of Obstetrics and Gynaecology, Monash University, Melbourne, VIC, Australia.,Department of Obstetrics and Gynaecology, Erasmus MC, University Medical Center, Rotterdam, Netherlands
| | - Marta Thio
- Women's Newborn Research Centre, The Royal Women's Hospital, Melbourne, VIC, Australia.,Centre of Research Excellence in Newborn Medicine, Murdoch Children's Research Institute, Melbourne, VIC, Australia.,Department of Obstetrics and Gynaecology, University of Melbourne, Melbourne, VIC, Australia
| | - Tessa Martherus
- Division of Neonatology, Department of Pediatrics, Leiden University Medical Center, Leiden, Netherlands
| | - Gary Ruben
- School of Physics and Astronomy, Monash University, Melbourne, VIC, Australia
| | - Charles C Roehr
- Newborn Services, John Radcliffe Hospital, Oxford University Hospitals, NHS Foundation Trust, Oxford, United Kingdom.,Medical Sciences Division, Department of Pediatrics, University of Oxford, Oxford, United Kingdom
| | - Sophie J E Cramer
- Division of Neonatology, Department of Pediatrics, Leiden University Medical Center, Leiden, Netherlands.,Department of Instrumental Affairs, Leiden University Medical Center, Leiden, Netherlands
| | - Andreas W Flemmer
- Department of Neonatology, Dr. v. Haunersches Kinderspital & Perinatal Center Grosshadern, Medical Center of the University of Munich, Munich, Germany
| | - Linda Croton
- School of Physics and Astronomy, Monash University, Melbourne, VIC, Australia
| | - Arjan B Te Pas
- Division of Neonatology, Department of Pediatrics, Leiden University Medical Center, Leiden, Netherlands
| | - Marcus J Kitchen
- School of Physics and Astronomy, Monash University, Melbourne, VIC, Australia
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Aulakh GK, Mann A, Belev G, Wiebe S, Kuebler WM, Singh B, Chapman D. Multiple image x-radiography for functional lung imaging. Phys Med Biol 2017; 63:015009. [PMID: 29116051 DOI: 10.1088/1361-6560/aa9904] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
Abstract
Detection and visualization of lung tissue structures is impaired by predominance of air. However, by using synchrotron x-rays, refraction of x-rays at the interface of tissue and air can be utilized to generate contrast which may in turn enable quantification of lung optical properties. We utilized multiple image radiography, a variant of diffraction enhanced imaging, at the Canadian light source to quantify changes in unique x-ray optical properties of lungs, namely attenuation, refraction and ultra small-angle scatter (USAXS or width) contrast ratios as a function of lung orientation in free-breathing or respiratory-gated mice before and after intra-nasal bacterial endotoxin (lipopolysaccharide) instillation. The lung ultra small-angle scatter and attenuation contrast ratios were significantly higher 9 h post lipopolysaccharide instillation compared to saline treatment whereas the refraction contrast decreased in magnitude. In ventilated mice, end-expiratory pressures result in an increase in ultra small-angle scatter contrast ratio when compared to end-inspiratory pressures. There were no detectable changes in lung attenuation or refraction contrast ratio with change in lung pressure alone. In effect, multiple image radiography can be applied towards following optical properties of lung air-tissue barrier over time during pathologies such as acute lung injury.
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Affiliation(s)
- G K Aulakh
- Small Animal Clinical Sciences, Western College of Veterinary Medicine, University of Saskatchewan, Saskatoon, Canada
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8
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Lovric G, Vogiatzis Oikonomidis I, Mokso R, Stampanoni M, Roth-Kleiner M, Schittny JC. Automated computer-assisted quantitative analysis of intact murine lungs at the alveolar scale. PLoS One 2017; 12:e0183979. [PMID: 28934236 PMCID: PMC5608210 DOI: 10.1371/journal.pone.0183979] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2017] [Accepted: 08/15/2017] [Indexed: 12/13/2022] Open
Abstract
Using state-of-the-art X-ray tomographic microscopy we can image lung tissue in three dimensions in intact animals down to a micrometer precision. The structural complexity and hierarchical branching scheme of the lung at this level of details, however, renders the extraction of biologically relevant quantities particularly challenging. We have developed a methodology for a detailed description of lung inflation patterns by measuring the size and the local curvature of the parenchymal airspaces. These quantitative tools for morphological and topological analyses were applied to high-resolution murine 3D lung image data, inflated at different pressure levels under immediate post mortem conditions. We show for the first time direct indications of heterogeneous intra-lobar and inter-lobar distension patterns at the alveolar level. Furthermore, we did not find any indication that a cyclic opening-and-collapse (recruitment) of a large number of alveoli takes place.
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Affiliation(s)
- Goran Lovric
- Centre d’Imagerie BioMédicale, École Polytechnique Fédérale de Lausanne, 1015 Lausanne, Switzerland
- Swiss Light Source, Paul Scherrer Institute, 5234 Villigen, Switzerland
- Institute for Biomedical Engineering, ETH Zurich, 8092 Zurich, Switzerland
| | - Ioannis Vogiatzis Oikonomidis
- Swiss Light Source, Paul Scherrer Institute, 5234 Villigen, Switzerland
- Institute of Anatomy, University of Bern, 3012 Bern, Switzerland
| | - Rajmund Mokso
- Max IV Laboratory, Lund University, SE-221 00 Lund, Sweden
| | - Marco Stampanoni
- Swiss Light Source, Paul Scherrer Institute, 5234 Villigen, Switzerland
- Institute for Biomedical Engineering, ETH Zurich, 8092 Zurich, Switzerland
| | - Matthias Roth-Kleiner
- Clinic of Neonatology, University Hospital of Lausanne (CHUV), 1011 Lausanne, Switzerland
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9
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Parvizi A, Broek WVD, Koch CT. Recovering low spatial frequencies in wavefront sensing based on intensity measurements. ACTA ACUST UNITED AC 2016. [DOI: 10.1186/s40679-016-0017-y] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
AbstractThe transport of intensity equation (TIE) offers a convenient method to retrieve the phase of a wave function from maps of the irradiance (images) recorded at different planes along the optic axis of an optical system. However, being a second-order partial differential equation, even for noise-free data a unique solution of the TIE requires boundary conditions to be specified which are generally not accessible experimentally, jeopardizing retrieval of the low-frequency information in particular. Here we introduce an iterative algorithm which forgoes the need for explicit boundary conditions and combines the well-known reciprocal space solution of the TIE with the charge-flipping algorithm that has originally been developed to solve the crystallographic phase problem in X-ray diffraction. Application of this algorithm to experimental data and comparison with conventionally used algorithms demonstrates an improved retrieval of the low spatial frequencies of the phase.
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10
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Kitchen MJ, Buckley GA, Leong AFT, Carnibella RP, Fouras A, Wallace MJ, Hooper SB. X-ray specks: low dose in vivo imaging of lung structure and function. Phys Med Biol 2015; 60:7259-76. [PMID: 26348552 DOI: 10.1088/0031-9155/60/18/7259] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Respiratory health is directly linked to the structural and mechanical properties of the airways of the lungs. For studying respiratory development and pathology, the ability to quantitatively measure airway dimensions and changes in their size during respiration is highly desirable. Real-time imaging of the terminal airways with sufficient contrast and resolution during respiration is currently not possible. Herein we reveal a simple method for measuring lung airway dimensions in small animals during respiration from a single propagation-based phase contrast x-ray image, thereby requiring minimal radiation. This modality renders the lungs visible as a speckled intensity pattern. In the near-field regime, the size of the speckles is directly correlated with that of the dominant length scale of the airways. We demonstrate that Fourier space quantification of the speckle texture can be used to statistically measure regional airway dimensions at the alveolar scale, with measurement precision finer than the spatial resolution of the imaging system. Using this technique we discovered striking differences in developmental maturity in the lungs of rabbit kittens at birth.
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Affiliation(s)
- Marcus J Kitchen
- School of Physics and Astronomy, Monash University, Clayton, Victoria, Australia
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11
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Leong AF, Buckley GA, Paganin DM, Hooper SB, Wallace MJ, Kitchen MJ. Real-time measurement of alveolar size and population using phase contrast x-ray imaging. BIOMEDICAL OPTICS EXPRESS 2014; 5:4024-38. [PMID: 25426328 PMCID: PMC4242036 DOI: 10.1364/boe.5.004024] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/02/2014] [Revised: 10/16/2014] [Accepted: 10/18/2014] [Indexed: 05/09/2023]
Abstract
Herein a propagation-based phase contrast x-ray imaging technique for measuring particle size and number is presented. This is achieved with an algorithm that utilizes the Fourier space signature of the speckle pattern associated with the images of particles. We validate this algorithm using soda-lime glass particles, demonstrating its effectiveness on random and non-randomly packed particles. This technique is then applied to characterise lung alveoli, which are difficult to measure dynamically in vivo with current imaging modalities due to inadequate temporal resolution and/or depth of penetration and field-of-view. We obtain an important result in that our algorithm is able to measure changes in alveolar size on the micron scale during ventilation and shows the presence of alveolar recruitment/de-recruitment in newborn rabbit kittens. This technique will be useful for ventilation management and lung diagnostic procedures.
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Affiliation(s)
| | | | | | - Stuart B. Hooper
- The Ritchie Centre MIMR-PHI Institute of Medical Research and the Department of Obstetrics and Gynaecology, Monash University, Vic 3168,
Australia
| | - Megan J. Wallace
- The Ritchie Centre MIMR-PHI Institute of Medical Research and the Department of Obstetrics and Gynaecology, Monash University, Vic 3168,
Australia
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